JP2001337240A - Device and method for manufacture of optical waveguide substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for manufacturing an optical waveguide substrate by which the surface of a substrate is efficiently oxidized in the process of manufacturing an optical waveguide substrate by oxidizing the surface of a silicon substrate to a relatively deep part at high temperature in a water vapor gas atmosphere. SOLUTION: The device 1 for the manufacture of an optical waveguide substrate is equipped with a heating furnace 17 disposed around a reactor core tube 18 in which a silicon substrate 15 for the formation of a quartz film on the substrate surface is mounted inside, and with a supply pipe 11 and a ventilation pipe 20 for the oxidative gas to oxidize the silicon substrate 15 and connected to the reactor core tube 18. A vaporizer 10 to vaporize hydrogen peroxide 9 to produce the oxidative gas is connected to the supply pipe 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for efficiently manufacturing an optical waveguide substrate used as an optical waveguide device for optical communication by oxidizing the surface of a silicon substrate to a relatively large thickness. It is.

[0002]

2. Description of the Related Art A waveguide device for optical communication includes an optical waveguide and a semiconductor integrated circuit. The semiconductor integrated circuit is formed on a silicon substrate. The oxide film required for the semiconductor integrated circuit is as thin as about 0.2 to 3 μm. On the other hand, the optical waveguide is formed on a quartz substrate. The quartz substrate is obtained by forming a quartz film, ie, silicon dioxide, on the surface of a silicon substrate. This film has a thickness of 5 to 30 since it functions optically as an under clad of the optical waveguide.
It is required to be very thick, about μm, as compared with the oxide film of the semiconductor integrated circuit.

One of the methods for forming such a quartz film for an optical waveguide or an oxide film for a semiconductor integrated circuit is that silicon constituting a substrate has a high affinity for oxygen and is easily oxidized. There is a method in which silicon on the substrate surface is oxidized into a quartz film by using the quartz film.

[0004] This method includes, for example, a dry oxygen oxidation method,
There are a wet oxidation method, a steam oxidation method, a hydrogen combustion oxidation method, and a hydrochloric acid oxidation method. There is also a method of oxidizing at a high pressure in order to shorten the time for forming an oxide film by increasing the oxygen partial pressure, or a method of oxidizing with a highly reactive oxidizing gas such as halogen gas or nitrogen oxide.

In the wet oxidation method, the steam oxidation method, and the hydrogen combustion oxidation method, a silicon substrate is heated to a high temperature in a furnace tube and brought into contact with steam at normal pressure, and the steam is thermally decomposed to form highly reactive oxygen. In addition, a silicon film is oxidized to form a quartz film, and the oxidation rate is relatively high. There is no need for equipment for collecting highly toxic halogen gas, etc.
It is widely used because the core tube does not need to be pressure-resistant.

A quartz film having a thickness of 0.2 to 3 μm required for a semiconductor integrated circuit is formed, for example, by a steam oxidation method to a thickness of 10 to
It is formed by exposing to a steam atmosphere at 1200 ° C. for a relatively short time of 1000 minutes. However, when forming a 10-25 μm quartz film commonly used for optical waveguides, 20 mm
There is a problem that it is necessary to expose to a steam atmosphere at 1200 ° C. for as long as 000 to 125000 minutes.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems. In manufacturing an optical waveguide substrate by oxidizing a relatively thick surface of a silicon substrate under a steam gas atmosphere at a high temperature, An object of the present invention is to provide a manufacturing apparatus and a manufacturing method of an optical waveguide substrate for efficiently oxidizing.

[0008]

In order to achieve the above object, an optical waveguide substrate manufacturing apparatus 1 according to the present invention has a core in which a silicon substrate 15 on which a quartz film is formed is placed. An apparatus for manufacturing an optical waveguide substrate, in which a heating furnace 17 is arranged on the outer periphery of a tube 18 and an oxidizing gas supply tube 11 for oxidizing the silicon substrate 15 and an exhaust tube 20 are connected to a furnace core tube 18, A vaporizer 10 for vaporizing the hydrogen water 9 to generate an oxidizing gas is connected to the supply pipe 11.

The vaporizer 10 has a heating device 8 for vaporizing.
Is provided, it can be suitably implemented.

[0010] Heat the hydrogen peroxide solution at 100 ° C or more.
The hydrogen peroxide gas evaporated with the steam gas by
When heated to a high temperature of 500 ° C. or more, the following chemical formula 2H₂O₂ → 2H₂O + O₂  Is decomposed as shown in
Occurs.

When the furnace core tube 18 in a steam gas atmosphere containing hydrogen peroxide gas is heated to 1000 to 1300 ° C.,
Due to the synergistic effect of the active oxygen generated by the decomposition of the steam gas and the active oxygen generated by the decomposition of the hydrogen peroxide gas, the oxidation rate of silicon on the surface of the silicon substrate is increased.

The hydrogen peroxide solution 9 in the vaporizer 10 is 20 to
Preferably, the concentration is 70%. If it is less than 20%, the concentration of hydrogen peroxide gas in the steam gas becomes so low that the reaction rate cannot be increased. If it is higher than 70%, there is a risk of explosion. More preferably, it is 30 to 60%.

The present invention can be suitably implemented by connecting the supply pipe 5 for supplying another hydrogen peroxide solution 2 filled in the tank 3 to the vaporizer 10 to the vaporizer 10.

The vapor pressure at the same temperature is higher in water than in hydrogen peroxide. Therefore, when the hydrogen peroxide solution 9 is heated by the vaporizer 10, the water evaporates in a larger amount than the hydrogen peroxide. Vaporizer 1
In order to prevent the hydrogen peroxide solution 9 in 0 from being gradually concentrated, about 15% of the hydrogen peroxide solution 2 is supplied to the vaporizer 10 from the tank 3. When a predetermined amount is supplied, the hydrogen peroxide solution 9 in the vaporizer 10 is maintained at a constant concentration.

In the method of manufacturing an optical waveguide substrate according to the present invention, a silicon substrate 15 having a quartz film formed on its surface is placed inside a furnace tube 18 having a heating furnace 17 disposed on the outer periphery thereof, and then a hydrogen peroxide solution is placed. The oxidizing gas generated by vaporizing 9 is supplied to the furnace tube 18 and heated in the heating furnace 17 to oxidize the surface silicon of the silicon substrate 15 with the oxidizing gas.

This manufacturing method can be suitably carried out because the vaporization is caused by heating. The heating temperature for vaporization is preferably from 110 to 150 ° C, and from 120 to 150 ° C.
The temperature is more preferably 140 ° C.

According to the method of manufacturing the optical waveguide substrate, the oxidation rate of silicon on the surface of the silicon substrate 15 is increased as compared with the case of oxidizing with pure steam gas. Therefore, the yield of the optical waveguide substrate is improved.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of an optical waveguide substrate manufacturing apparatus 1 to which the present invention is applied.

In this manufacturing apparatus 1, a heating furnace 17 is disposed around a furnace tube 18 made of silicon carbide having high heat resistance. The inner surface of the furnace tube 18 is coated with a silicon carbide film of several μm by chemical vapor deposition. One end of the furnace tube 18 is substantially closed, and is connected to a supply tube 11 for supplying a steam gas containing a hydrogen peroxide gas. On-off valve 1 for controlling gas supply in the middle of the path of gas supply pipe 11
2 are arranged. The gas supply pipe 11 is connected to the vaporizer 10. The vaporizer 10 has a configuration in which a heater 8 as a heating device is arranged outside a container 7 containing a 50% hydrogen peroxide solution 9. The container 7 is covered with an upper lid 6 through which the gas supply pipe 11 and the hydrogen peroxide water supply pipe 5 penetrate. In the container 7, the tip of the gas supply pipe 11 is arranged higher than the liquid surface of the hydrogen peroxide solution 9, and the tip of the hydrogen peroxide solution supply pipe 5 reaches the liquid of the hydrogen peroxide solution 9. The other end of the hydrogen peroxide solution supply pipe 5 is inserted into the tank 3 and reaches the 15% hydrogen peroxide solution 2 filled in the tank 3. A pump 4 is provided in the middle of the supply pipe 5.

The other end of the furnace tube 18 is covered with a lid 19 to which an exhaust pipe 20 is attached. A temperature sensor 14 composed of a thermocouple is arranged inside the furnace tube 18.
The temperature sensor 14 is connected to a temperature display device (not shown). A sample table 16 made of silicon carbide is provided with three cut grooves. A sample table 16 on which a silicon substrate 15 is inserted and placed in the cut groove is placed inside a furnace tube 18. The core tube 18 is inserted into the protective container 13.

An optical waveguide substrate is manufactured using this apparatus 1 as follows. Three disk-shaped silicon substrates 15 made of silicon are inserted into the cut grooves of the sample table 16 and are arranged at equal intervals.

In order to prevent foreign matter from adhering to the silicon substrate 15 due to static electricity, the furnace tube 1 is previously heated by the heating furnace 17.
8 is heated slowly, and the temperature in the
500 ° C. The sample stage 16 is inserted from the open end of the furnace tube 18, and placed in the furnace tube 18, and the open end is covered with a lid 19. The furnace tube 18 is further heated until the internal temperature of the furnace tube 18 reaches a predetermined temperature of 1000 to 1300 ° C. When a predetermined temperature is reached, the on-off valve 12 is opened.

Then, the heater 8 of the vaporizer 10 is set to 10
0 to 130 ° C. and heat the hydrogen peroxide solution 9 in the container 7
Steam containing hydrogen peroxide gas vaporized by heating
Gas gas flows into the core tube 18 via the gas supply tube 11.
No. Since the temperature in the furnace tube 18 is high, the steam gas is thermally decomposed.
To generate active oxygen and pyrolyze hydrogen peroxide gas to activate
Produces oxygen. The surface silicon of the silicon substrate 15 is
The oxygen has the following chemical formula: Si + O₂ → SiO₂  To form a quartz film.

A concentration rate of the hydrogen peroxide solution when the hydrogen peroxide solution 9 in the container 7 of the vaporizer 10 is heated at a certain temperature is measured in advance, and the concentration rate of the hydrogen peroxide solution in the container 7 is determined based on the concentration rate. Hydrogen peroxide solution 9 of a predetermined concentration which must be replenished in order to keep the hydrogen peroxide solution 9 at a constant concentration.
The supply amount per unit time of the 5% hydrogen peroxide solution is uniquely calculated. The pump 4 is driven to supply the calculated amount of the hydrogen peroxide solution 2 from the tank 3 filled with the 15% hydrogen peroxide solution 2 into the container 7.

When a quartz film having a desired thickness is formed, the on-off valve 12 is closed to stop the supply of the steam gas containing the hydrogen peroxide gas. At the same time, the heating of the hydrogen peroxide solution by the heater 8 and the replenishment of the hydrogen peroxide solution 2 from the tank 3 are stopped. The core tube 18 is cooled slowly. The sample stage 16 is pulled out to obtain an optical waveguide substrate in which quartz films are formed on both surfaces of a silicon substrate.

An example in which an optical waveguide substrate is prototyped using a manufacturing apparatus to which the present invention is applied will be described below in Example 1.
An example in which an optical waveguide substrate is prototyped using a manufacturing apparatus to which the present invention is not applied is described in Comparative Example 1.

(Embodiment 1) A diameter of 4 inches and a thickness of 0.6 m
A part of the outer circumference of the silicon disk-shaped silicon substrate 15 of m is flattened. The three silicon substrates 15 are inserted into the grooves on the sample stage 16 and are arranged at equal intervals with the flat part facing upward. 5 so that the core tube 18 is not damaged by sudden temperature changes.
The furnace tube 18 is heated by the Kanthal heater tubular furnace, which is the heating furnace 17, at a gradual heating rate of ° C / min. When the inside of the furnace tube 18 reaches 500 ° C., the sample table 16 is inserted and placed inside the furnace tube 18, and then the lid 19 having the exhaust pipe 20 is inserted.
Cover with. The temperature is further increased until the inside of the furnace tube 18 reaches 1200 ° C.

On the other hand, the heater 8 of the vaporizer is set at 130 ° C. to heat the 50% hydrogen peroxide solution in the container. At the same time, the pump 4 is driven to supply 0.1 L / hour of 15% hydrogen peroxide water 2 from the tank 3 to the container for 1 L of 50% hydrogen peroxide water 9 in the container.

When the temperature in the furnace tube 18 reaches 1250 ° C., the on-off valve 12 of the gas supply tube 11 is opened. Then, the steam gas containing the hydrogen peroxide gas vaporized by heating the hydrogen peroxide solution 9 is passed through the gas supply pipe 11 to the reactor core tube 1.
Flow into 8. In the furnace tube 18, active silicon generated by the thermal decomposition of hydrogen peroxide gas and water vapor gas oxidizes the surface silicon of the silicon substrate 15 to form a quartz film. Oxidation is carried out at this temperature for 10,000 minutes while the supply of the hydrogen peroxide gas and the steam gas is continued. Thereafter, the furnace tube 18 is cooled. At the same time, the on-off valve 12 is closed, and the heating by the heater 8 and the driving of the pump 4 are stopped.
When the sample stage 16 is pulled out, both surfaces of the silicon substrate 15
An optical waveguide substrate on which a 15 μm-thick quartz film is formed is obtained.

(Comparative Example 1) 5 in a vaporizer container
Except that pure water was used in place of 0% hydrogen peroxide and pure water was supplied from a tank,
An optical waveguide substrate was prototyped. It took 12,000 minutes to form a quartz film having the same thickness as the optical waveguide substrate obtained in Example 1.

The relationship between the thickness of the quartz film formed by oxidizing the surface silicon of the silicon substrate according to the first embodiment and the oxidation time required for the formation is shown by the solid line in FIG. Also,
The relationship between the thickness of the quartz film formed according to Comparative Example 1 and the oxidation time is shown by the broken line in FIG. As is clear from the comparison between the two in FIG. 2, the oxidation speed is faster in the case of oxidizing according to Example 1 than in the case of oxidizing according to Comparative Example 1, so that the time required to obtain a desired quartz film thickness is shorter.

Next, in order to clarify the difference in the oxidation rate when the temperature of the heater of the vaporizer was variously changed, the surface silicon of the silicon substrate was oxidized by generating a steam gas containing hydrogen peroxide gas. Examples are shown in Examples 2 to 4. Comparative examples 2 to 4 show examples in which only water vapor was generated to oxidize the surface silicon of the silicon substrate for comparison.

(Examples 2 to 4) The oxidation time was set to 180 minutes, and the temperature of the heater of the vaporizer was set to 100 ° C and 120 ° C.
The surface silicon of the silicon substrate was oxidized in the same manner as in Example 1 except that the temperature was set to 130 ° C. and 130 ° C. Table 1 shows the results of measuring the thickness of the quartz film formed on the silicon substrate.

(Comparative Examples 2 to 4) The oxidation time was set to 180 minutes, and the temperature of the heater was set to 100 ° C., 120 ° C., and 130 ° C. using pure water instead of the hydrogen peroxide solution in the vaporizer. Example 1 except that pure water was supplied from the tank.
The silicon substrate was oxidized in the same manner as described above. Table 1 shows the results of measuring the thickness of the quartz film formed on the silicon substrate.

[0035]

[Table 1]

As shown in Examples 2 to 4 in Table 1, those oxidized using aqueous hydrogen peroxide have a higher quartz film thickness as the heating temperature of the heater is higher, if the oxidation time is constant. . On the other hand, as shown in Comparative Examples 2 to 4, those oxidized using pure water had almost no change in the quartz film thickness due to the difference in the heating temperature of the heater. As is clear from the comparison between Example 4 and Comparative Example 4 in Table 1, if the oxidation time and the heating temperature of the heater are constant, the oxidation time is higher than in the case where pure water is heated and oxidized with steam generated. Since the oxidation rate is faster when oxidizing with steam gas containing hydrogen peroxide gas generated by heating the hydrogen oxide water, the obtained quartz film is thicker.

[0037]

As described above, when an optical waveguide substrate is manufactured using the manufacturing apparatus of the present invention, oxidation can be efficiently performed. Further, the yield of the optical waveguide substrate is good. The use of steam gas and hydrogen peroxide gas for the production makes it highly safe. Since the obtained optical waveguide substrate is of high quality, an optical waveguide device having excellent performance can be formed using this optical waveguide substrate.

[Brief description of the drawings]

FIG. 1 is a schematic view of an optical waveguide substrate manufacturing apparatus to which the present invention is applied.

FIG. 2 is a graph showing the relationship between the thickness of a quartz film formed by oxidizing surface silicon of a silicon substrate and the oxidation time required for formation.

[Explanation of symbols]

1 is an optical waveguide substrate manufacturing apparatus, 2 is a hydrogen peroxide solution, 3 is a tank, 4 is a pump, 5 is a hydrogen peroxide solution supply pipe, 6 is a top lid, 7 is a container, 8 is a heater, and 9 is hydrogen peroxide. Water, 10 is a vaporizer, 11 is a gas supply pipe, 12 is an on-off valve, 13 is a protection container, 14 is a temperature sensor, 15 is a silicon substrate, 16 is a sample stage, 17 is a heating furnace, 18 is a furnace tube, and 19 is a furnace tube. Lid, 20
Is an exhaust pipe.

Continued on the front page (72) Inventor Masaaki Shiroda 2-3-1-1, Isobe, Annaka-shi, Gunma Shin-Etsu Kagaku Kogyo Co., Ltd. Precision Functional Materials Laboratory (72) Inventor Masatake Ejima 2--13 Isobe, Annaka-shi, Gunma No.1 Shin-Etsu Kagaku Kogyo Co., Ltd. Precision Functional Materials Laboratory F-term (reference) 2H047 PA01 QA04 QA07 TA42

Claims (6)

[Claims] 1. A heating furnace is arranged around a furnace tube in which a silicon substrate on which a quartz film is formed is placed, and a supply tube and an exhaust tube for an oxidizing gas for oxidizing the silicon substrate are provided. An apparatus for manufacturing an optical waveguide substrate connected to the furnace tube, wherein a vaporizer for vaporizing hydrogen peroxide to generate the oxidizing gas is connected to the supply tube. Substrate manufacturing equipment. 2. The apparatus according to claim 1, wherein the vaporizer is provided with a heating device for performing the vaporization. 3. The optical waveguide according to claim 1, wherein a supply pipe for supplying another hydrogen peroxide solution filled in a tank to the vaporizer is connected to the vaporizer. Substrate manufacturing equipment. 4. A silicon substrate on which a quartz film is to be formed is placed inside a furnace tube in which a heating furnace is disposed on the outer periphery, and then an oxidizing gas generated by evaporating hydrogen peroxide is added to the core. A method for producing an optical waveguide substrate, wherein the surface silicon of a silicon substrate is oxidized with the oxidizing gas by heating in a heating furnace while supplying to a tube. 5. The method for manufacturing an optical waveguide substrate according to claim 4, wherein said vaporization is caused by heating. 6. The heating temperature of the vaporization is 110 to 150 ° C.
The method of manufacturing an optical waveguide substrate according to claim 5, wherein